Fan control module for a system unit

ABSTRACT

A fan control module is provided for a system unit. The fan control module includes power outputs for supplying power to a plurality of fan. It also includes a temperature sensor for giving a temperature signal. It further includes a control unit connected to receive the temperature signal and including preprogrammed control information for determining power signals to be supplied to each of the fan units for controlling the speed thereof. The fan control module can control the fan units in a coordinated manner enabling reliable and effective cooling of the system unit under widely varying parameters. It can mean that existing system components can be employed in harsher temperature environments that they were originally designed for, without needed a complete redesign thereof. The fan control module can be provided with electrical noise isolation circuitry to isolate other components from electrical noise generated by the fan units. The system unit can, for example, be a computer system unit for rack mounting in a telecommunications application.

BACKGROUND OF THE INVENTION

[0001] The invention relates to cooling system units. In particular, theinvention relates to providing controlled cooling for a computer systemfor use in environments and applications that place high demands onsystem reliability, for example in the telecommunications industry.

[0002] Deregulation and privatization is causing unprecedentedcompetition in the worldwide telecommunications market. This climate offierce competition has meant that service providers must introduce new,more sophisticated and user-friendly services at an accelerated pace toretain or attract subscribers, while not compromising traditionaltelecommunications company (telco) service quality.

[0003] These pressures of competition have also placed high demands onNetwork Equipment Providers (NEPs). Traditionally, NEPs have designed,built and supported proprietary computing equipment, as the strict telcorequirements could not be met by the commercial computing sector. Thoserequirements include the so-called Telcordia Technologies NetworkEquipment Buildings Systems (NEBS) tests. However, due to the lead timesrequired to design and test such proprietary equipment, and the cost ofsupporting such equipment, there is a need to find another route, atleast for the supply of the more cost and performance sensitive sectorswithin the telco industry.

[0004] A major concern of the telco sector is the reliability of systemsunder environment conditions as set by the NEBS tests.

[0005] In order to keep up with the ever-increasing demands of the telcoindustry, and in order to provide equipment at reasonable cost andwithin reasonable time scales, it would be desirable to use as manyoff-the-shelf computer system components as possible, rather than havingto design and test each system in its entirety from scratch. Forexample, it would be desirable to select components designed for thecommercial computing sector. However, such equipment is typically notdesigned with the stringent requirements of the telco industry in mind.

[0006] Accordingly, it is an aim of the present invention to address theprovision of cost-effective equipment that can meet technical demands ofthe telco environments, for example as regards providing reliableoperation under adverse operating temperatures, while also meeting themodem commercial demands of that environment.

SUMMARY OF THE INVENTION

[0007] Particular and preferred aspects of the invention are set out inthe accompanying independent and dependent claims. Combinations offeatures from the dependent claims may be combined with features of theindependent claims as appropriate and not merely as explicitly set outin the claims.

[0008] In accordance with one aspect of the invention, there is provideda fan control module for a system unit. The fan control module comprisespower outputs for supplying power to a plurality of fan. It alsoincludes a temperature sensor for giving a temperature signal. Itfurther includes a control unit connected to receive the temperaturesignal. The control unit includes preprogrammed control information fordetermining power signals to be supplied to each of the fan units forcontrolling the speed thereof dependent upon the temperature signal.

[0009] The provision of a separate fan control module for controllingthe fan units in a coordinated manner enables reliable and effectivecooling of the system unit under widely varying parameters. It alsomeans that existing system components can be employed in harshertemperature environments than they were originally designed for, withoutneeding a complete redesign thereof.

[0010] Moreover, where the fan control module includes one or more powerinputs from a power supply that is also used to power the othercomponents of the system unit, the fan control module can be providedwith electrical noise isolation circuitry to isolate other components ofthe system unit, from electrical noise generated by the fan units.

[0011] In order to limited the power handling requirements of the fancontrol module circuits, in an embodiment of the invention the fancontrol module can be logically split into two parts. A first partcontrols a first pair of fan units and the second part controls a secondpair of fan units. Each part of the fan control module can be providedwith respective inputs, outputs and control units. The controlinformation programmed in the control unit of each part can beidentical. Preferably, one temperature sensor is be employed by bothparts to provide a co-ordinated ramp for the fan speeds. Also, wheremore than four fans are provided, more than two fans per part could becontrolled and/or more parts could be employed, as appropriate.

[0012] The fan control module is preferably configured on a singlecircuit board. This provides particular advantages where the fan controlcard is to be provided as an addition to a system. The temperaturesensor is preferably mounted on the circuit board, although it could beplaced at some another part of the system as appropriate. Preferably onetemperature sensor is used as this facilitates the provision of acontrolled and coordinated ramp up of the fan speeds. However, more thanone temperature sensor could be used, if desired, with each temperaturesensor providing respective signals and control of the individual fansbeing dependent upon individual temperature signals or a function ofsome or all of the temperature signals.

[0013] Preferably speed signals, for supply to an alarms module, aredirected via the fan control module and a power distribution board. Thefan control module does not process these signals, but the feeding ofthe signals via the fan control module enables an efficient wiring loomto be made, with a single bundle of wires and a single connector beingconnected to a fan unit.

[0014] In accordance with another aspect of the invention, there isprovided a system unit including a fan control module, the fan controlmodule comprising power outputs for supplying power to a plurality offan units, a temperature sensor for giving a temperature signal, and acontrol unit connected to receive the temperature signal and includingpreprogrammed control information for determining power signals to besupplied to each of the fan units for controlling the speed thereofdependent upon the temperature signal.

[0015] In a particular embodiment the system unit is a computer systemunit including at least one processor module. It may contain anywherebetween one and four processor modules. This puts further demands on thecooling requirements, as these will vary in accordance with the numberof processors present. Accordingly, the power supply signals output bythe control unit can be made dependent upon to the number of processormodules present.

[0016] In accordance with a further aspect of the invention, there isprovided a method of controlling cooling of a system unit, the methodcomprising:

[0017] a fan control module receiving a temperature signal from atemperature sensor;

[0018] the fan control module determining power outputs to the fan unitsfor controlling the speed thereof dependent upon the temperature signalfrom the temperature sensor and preprogrammed control information fordetermining power signals to be supplied to each of the fan units forcontrolling the speed thereof.

[0019] In the particular embodiment mentioned above, the system unit isa computer server intended to be rack-mounted for a telecommunicationsapplication. It will be appreciated that this puts further strain on thecooling requirements, due to different possible configurations ofadjoining equipment in a particular installation, and the possibleproximity of other heat generating elements. It will be appreciated thatthe present invention provides particular and important technicaladvantages when applied to the adaptation of systems to meet the strictreliability and temperature requirements of, for example,telecommunications applications and that it is ideally suited to suchtelecommunications applications.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Exemplary embodiments of the present invention will be describedhereinafter, by way of example only, with reference to the accompanyingdrawings in which like reference signs relate to like elements and inwhich:

[0021]FIG. 1 is a perspective view from the front of an embodiment ofthe invention including sacrificial transport brackets;

[0022]FIGS. 2A and 2B are plan and front views, respectively of theembodiment of FIG. 1 with alternative mounting brackets, and FIG. 2C isa side view showing the mounting holes for alternative types of mountingarrangements;

[0023]FIG. 3 is perspective view from the rear of the embodiment FIGS. 1and 2 illustrating a removable top cover;

[0024]FIG. 4 is an exploded view of the aforementioned embodiment;

[0025]FIG. 5 is a front view of the aforementioned embodiment;

[0026]FIG. 6 is a rear view of the aforementioned embodiment;

[0027]FIG. 7 is a plan view of a computer motherboard;

[0028]FIG. 8 is schematic block diagram of and example of thearchitecture of an embodiment of the invention;

[0029]FIG. 9 is perspective view from the rear of the embodiment FIGS. 1and 2 illustrating the removal of a power supply unit;

[0030]FIGS. 10A, 10B, 10C and 10D are rear, top, front and perspectiveviews of a power sub-frame for receiving three power supply unit, andFIG. 10E illustrates connections for various connectors of a powersub-frame assembly;

[0031]FIG. 11 is a schematic diagram of circuitry from a powerdistribution board of the power sub-frame of FIG. 10;

[0032]FIG. 12 illustrates the location of an alarm circuit;

[0033]FIG. 13 is a schematic block diagram of the logic of the alarmcircuit; and

[0034]FIG. 14 is a schematic diagram illustrating the configuration of afan control module.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] In the following, a particular embodiment of the invention willbe described by way of example only.

[0036]FIG. 1 is a perspective view of a system unit 10 for use in arack-mountable system. In a particular example described herein, thesystem unit is a computer system unit for forming a computer server fora telecommunications application, for example an Internet server. Asshown in FIG. 1, the unit 10 has a front surface 12 formed by a frontwall, a rear surface 14 formed by a rear wall, a left end surface 16formed by a left side wall, a right end surface 18 formed by a rightside wall, a lower surface 20 formed by a base wall and an upper surface22, in the present example formed by a cover 30. As shown in FIG. 1, thesystem unit 10 is provided with sacrificial transport flanges 24, whichextend above and below the system unit. This optional feature is removedbefore installation of the system unit 10 in a rack.

[0037] The system unit 10 is constructed with an extremely robustchassis 11, with the various walls 12-20 and the cover 30 forming thecasing of the chassis 11 as well as internal walls (not shown) beingformed of heavy gauge steel. The walls of the chassis can be made, forexample, from electroless nickel-plated mild steel with a thickness of,for example, 1.5 to 2.0-mm.

[0038] The steel chassis 11 is pre-formed with mounting holes for theattachment of mounting flanges or a slide mechanism to enable the systemunit 10 to be provided with a wide variety of mounting options and racksizes. Mounting flanges can be provided to suit standard 19-inch,23-inch, 24-inch or 600-mm nominal frame widths. (One inch=approximately25.4 mm).

[0039]FIG. 2A is a plan view of the unit 10 showing the upper surface22/cover 30 and various options for flanges 26 with the displacementsfrom the front surface indicated in mm.

[0040]FIG. 2B is a front view of the unit 10 showing the front surface12 and two different examples of mounting flanges 26. The mountingflange shown to the left (as seen in FIG. 2B) is provided with a handleto facilitate insertion and removal of the unit 10 from the rackingsystem, whereas the flange 26 to the right (as viewed in FIG. 2B) is notprovided with a handle.

[0041] In the present example, the mounting flanges can be attachedusing screws which pass through the mounting flange into threaded holesin the end walls 14, 16 at either side of the chassis 11 of the unit 10.FIG. 2C is a side view of the system unit 10, showing the holes in theside of the system unit 10 for the mounting of flanges or a slidemechanism. Vertical rows of holes are for the attachment of flanges tobe attached to vertical rack components, and horizontal rows of holesprovide for the attachment of a runners for permitting a slideablemounting of the system unit in a rack.

[0042]FIG. 3 is a perspective rear view of the unit 10 showing the cover30 that forms the top surface 22 of the unit 10. As can be seen, thecover 30 is provided with front locating flanges 32 that, in use, engagea co-operating front flange 31 of the body of the chassis 11. Sideflanges 33 engage either side of the end walls forming the left andright ends 16 and 18 of the chassis 11. Detents 34 on those end wallsengage within L-shaped slots 35 in the side flanges 33 so that the covermay be lowered onto the top of the chassis 11 and then moved forwards soas to cause the detents 34 to latch within the slots 35. At the rear ofthe cover 30, a rear flange 36 with a lower lip 37 engages over anabutment 38 at the top of the rear end wall 14 of the casing 10. Thecover can be secured to the remainder of the chassis 11 by means of ascrew 39 that passes through this rear flange into a threaded hole inthe abutment 38.

[0043]FIG. 4 is an exploded perspective view from the front of thesystem unit 10. This shows a motherboard 40 that is mounted on ahorizontal mounting plane 41 within the chassis 11. Mounted on themotherboard 40 are between one and four processor modules 42. A risercard 44 can receive a plurality of dual in-line memory modules (DIMMs)46. Further DIMMs 46 can be received directly in slots in themotherboard. A slideable carriage 48 is provided for receiving one ormore media drives.

[0044] As shown in FIG. 4, the slideable carriage 48 can receive up totwo media drives. In the present instance, two media drives including adigital audio tape (DAT) drive 50 and a CD-ROM drive 52 are provided.Appropriately configured metal cover plates 54 and 56 are provided forthe media drives 50 and 52. A disc bay assembly 58 provides a smallcomputer system interface (SCSI) backplane and cables for receiving oneor more SCSI media drives, such as a SCSI disc drive 60. Although, inthe present instance, the drives are controlled via a SCSI-typeinterface, it will be appreciated that another media drive interface(e.g., IDE) could be used. A SCSI card (not shown) is located within thechassis to the front of the motherboard. A bezel (decor panel) 62 isprovided for covering ventilation holes 63 in the front wall 12 of thechassis 11. A bezel 64 is provided for covering the media drives 50, 52and 60.

[0045] A fan control module 66 controls the operation of processor fans68 and system fans 70. A power sub-assembly that includes a powersub-frame 72 with a power distribution board assembly, is provided forreceiving three separate power supply units 74. An alarms module in theform of an alarms card 78 enables the signalling of alarms to theoutside world, and is also connected to an LED card 2 for signallingalarms locally on the front of the unit 10. A power switch 82 is alsoprovided on the front surface of the unit 10. FIG. 4 also illustratesone PCI card 84 to be received within a PCI slot 85 on the motherboard40.

[0046]FIG. 5 is a front view of the unit 10 showing the bezels 62 and64, a power and alarm panel 90 which includes the power switch 82 and anumber of status light emitting diodes (LEDs) 92. FIG. 5 alsoillustrates the slots 86 and 88 for the media drives such as mediadrives 50 and 52 shown in FIG. 4.

[0047]FIG. 6 is a rear view of the unit 10 in a configuration with threeDC power supply units 74A, 74B and 74C. Each of the power supply units74A, 74B and 74C is the same, and provides redundant power for the unit10. However, as will be seen later, one or more of the DC power supplyunits could be replaced by AC (mains) power supply units. The powersupplies are hot swappable (i.e., while the system is running), as longas they are swapped one at a time.

[0048] With regard to power supply unit 74A, it can be seen that this isprovided with a handle 94 that is used for inserting and removing thepower supply unit 74A. The handle 94 includes a flange portion that isable to receive a screw 95 for securing the power supply unit to thechassis 11. First and second power cable sockets 96 and 98 are shown.

[0049] Also shown is a grounding plate 100 that is secured by knurlednuts 102, 104 and 106 to grounding studs 103, 105 and 107. Groundingstud 103 provides a connection directly to the chassis 11 of the unit10. Grounding studs 105 and 107, on the other hand are electricallyisolated from the chassis by an insulating board and are insteadconnected to logic ground (i.e. the ground of the electronic circuitry).By means of the grounding plate 100, logic ground can be connecteddirectly to chassis ground. The provision of this grounding plateprovides for optional tying of logic ground to chassis ground. It willbe noted that each of the power supply units 74 is provided with asimilar grounding plate 100, for connection to corresponding groundingstuds. If it is desired to isolate logic ground from chassis ground, itis necessary to remove the grounding plate 100 from each of the powersupply units 74A, 74B and 74C.

[0050] An isolated ground system is needed in some telco applicationswhen operating in a Regional Bell Operating Company (RBOC) mode. Whenoperating in such a mode, the chassis and logic ground are connected ata remote location to provide, for example, lightning protection. In thiscase two-hole lugs 101 having a pair of holes 111 to fit over the pairof grounding studs 105 and 107 are provided for each of the power supplyunits 74 and are secured over the studs using nuts 104 and 106. Asimilar two-hole lug 101 is secured to the grounding studs 108 and issecured with similar nuts. Earthing wires 109 from each of the two-holelugs 101 on the power units and the chassis then are taken to theremote, earthing location. The studs 103 105, 107 and 108 are of astandard thread size (M5). The studs 105/107 and the studs 108 are at astandard separation (15.85 mm). The studs 105/107 are self-retaining inthe insulated board on the power supply units. The stud 103 isself-retaining in the casing of its power supply unit 74. The suds 108are also self-retaining in the system unit chassis.

[0051] In a non-isolated ground situation, chassis ground can simply betied to a desired ground potential (for example, to the racking system)by connecting a grounding cable to grounding studs 108 provided on therear of the chassis. A further earth connection is provided via thepower cables for the power supplies.

[0052]FIG. 6 also illustrates rear ventilation holes 110 through whichair is vented from the system. FIG. 6 also shows the alarms module 78with a serial connector 112 enabling connection of the alarms module toa network for the communication of faults and/or for diagnosticoperations on the unit 10 to be performed from a remote location. FIG. 6also shows a number of PCI cards 84 received within respective PCI slots116. A number of further external connections 114 are provided forconnection of serial connections, parallel connections and SCSIconnections, and for the connection of a keyboard or a Twisted-PairEthernet (TPE) connector.

[0053]FIG. 7 is a plan view of the motherboard 40 shown in FIG. 4. FourCPU module slots 120 are provided. Each of these slots is able toreceive one processor module 42, and any number between one and fourslots may be occupied by a processor module 42. A connector arrangement122 is provided for receiving a riser card 44 as shown in FIG. 4. Also,connectors 124 (in four banks) are provided for receiving DIMMs 46 asmentioned with reference to FIG. 4. Edge connectors 126 are provided forconnecting the motherboard to connectors mounted on the mounting plane41. Also shown in FIG. 7 is the slot 128 for the alarms module 78 andvarious ports 130 for the connectors 114 shown in FIG. 6.

[0054]FIG. 8 is a schematic overview of the computer architecture of thesystem 10. As shown in FIG. 8, various components within the system areimplemented through application-specific integrated circuits (ASICs).The system is based round a UltraSparc Port Architecture (UPA) bussystem that uses a Peripheral Component Interconnect (PCI) protocol foran I/O expansion bus. The CPU modules 40.0, 40.1, 40.2, 40.3, and aUPA-TO-PCI (U2P) ASIC 154 communicate with each other using the UPAprotocol. The CPU modules 40 and the U2P ASIC 154 are configured as UPAmaster-slave devices. An Address Router (AR) ASIC 154 routes UPA requestpackets through the UPA address bus and controls the flow of data to andfrom memory 150 using a Data Router (DR) ASIC 144 and a switchingnetwork 148. The AR ASIC 154 provides system control. It controls theUPA interconnect between the major system components and main memory.

[0055] The DR ASIC 144 is a buffered memory crossbar device that acts asa bridge between six system unit buses. The six system unit busesinclude two processor buses, a memory data bus and to I/O buses. The DRASIC 144 provides crossbar functions, memory port decoupling, bursttransfer and First-in-First-Out (FIFO) data read functions. Clockcontrol for the operation of the processor is provided by a Reset,Interrupt, Scan and Clock (RISC) ASIC 152.

[0056] The PCI bus is a high performance 32-bit or 64-bit bus withmultiplexed address and data lines. The PCI bus provides electricalinterconnection between highly integrated peripheral controllercomponents, peripheral add-on devices, and the processor-memory system.A one-slot PCI bus 155 connects to a PCI device 156.0. A three-slot PCIbus connects to three PCI slots 156.1, 156.2 and 156.3. Two controllersare also connected to the second PCI bus 157. These include a SCSIcontroller 174 and a PCI-TO-EBus/Ethernet controller (PCIO) 158. TheSCSI controller 174 provides electrical connection between themotherboard and separate internal and external SCSI buses. Thecontroller also provides for SCSI bus control. The PCIO 158 connects thePCI bus to the EBus. This enables communication between the PCI bus andall miscellaneous I/O functions as well as the connection to slower, onboard functions. Thus, the PCIO enables the connection to an Ethernetconnection via a Transmit/Receive (Tx/Rx) module 161 and a networkdevice (ND) module 162.

[0057] An EBus2 159 provides a connection to various I/O devices andinternal components. Super I/O 164 is a commercial off-the-shelfcomponent that contains two serial port controllers for keyboard andmouse, an IEEE 1284 parallel port interface and an IDE disk interface.The super I/O drives the various ports directly with someelectromagnetic interference filtering on the keyboard and parallel portsignals. The alarms module 78 interfaces with the motherboard andprovides various alarm functions. The NVRAM/TOD 168 providesnon-volatile read only memory and the time of day function. Serial port170 provides a variety of functions. Modem connection to the serial port170 enables access to the Internet. Synchronous X.25 modems can be usedfor telecommunications in Europe. An ASCII text window is accessiblethrough the serial port on non-graphics systems. Low speed printers,button boxes (for computer aided design applications) and devices thatfunction like a mouse are also accessible through the serial port. Theserial port includes a serial port controller, line drivers and linereceivers. A one-Mbyte flash programmable read only memory (PROM) 172provides read only memory for the system.

[0058]FIG. 9 is a perspective rear view of the system 10 showing thewithdrawal and/or insertion of a power supply unit 74 in a non-isolatedground situation. In this example, AC power supply units 74 are shown.It can be seen that the power supply unit 74 is provided with the handle94. As shown in FIG. 9, the handle 94 is provided with a grip 184, apivot 182 and a latch 180. To insert the power supply unit 74 it isnecessary to slide the power supply unit into the power sub-frame 72with the grip 184 of the handle 94 slightly raised so that the detent180 can be received under the top 184 of the power sub-frame 72. As thepower supply unit 74 reaches the end of its movement into the powersub-frame 72, connectors (not shown) provided on the power supply unit74 make connection with a corresponding connector on the powerdistribution board at the rear of the power sub-frame 72. Also, at thistime, the handle can be pushed down into the position shown in FIG. 9.This causes the detent 180 to latch behind the upper portion 184 of thepower sub-frame 72. The handle 94 can then be secured in place bytightening the screw 95. The AC power supply unit 74 shown in FIG. 9 hasa single power socket 97, whereas the DC power supply units 74 shown inFIG. 6 have two power sockets 96 and 98. Irrespective of whether thearrangement is as shown in FIG. 6 with two DC power sockets 96 and 98,or as shown in FIG. 9 with one AC power socket 97, the configuration ofthe power socket(s) and the lever 94 is such that the lever cannot bemoved, and therefore the power supply unit cannot be released from thepower sub-frame 72 and the chassis 11 with a plug 186 of a power cable188 in place in one of the power sockets 96/97/98. The removal operationis achieved by releasing the screw 95, removing the power plug, andlifting and pulling on the handle 94.

[0059] In an isolated ground situation, in order to hot-swap a powersupply unit 74, it is merely necessary to remove the two-hole lug 101with its connecting earth wire 109 from the studs 105, 107 of the powersupply unit to be removed, to remove the old power supply unit 74, toreplace a new power supply unit 74 and then to reconnect the two-holelug 101 and connecting earth wire 109 to the studs 105, 107 of the newpower supply unit 74. These operations can all be performed with thesystem under power from the other power supply units 74 and with thetwo-hole lugs 101 and earth wires 109 in place over the chassis studs108 and the studs 105, 107 of the other power supply units 74.

[0060] The isolated ground situation is not shown in FIGS. 6 and 9. Inthe non-isolated ground situation shown in FIGS. 6 and 9, hot-swappingof a power supply unit is even easier, as it is merely necessary toremove the selected power supply unit 74 and to replace it with the newpower supply unit 74.

[0061]FIGS. 10A, 10B, 10C and 10D are rear, top, front and perspectiveviews of a power sub-frame for receiving three power supply units:

[0062] The power sub-frame 72 comprises a rectangular, box-shaped frame191, with four exterior walls on four sides (the top, bottom and twolateral surfaces), one open side 195 for receiving three power supplyunits and a power distribution circuit board 190 opposite to the openside. In the present instance, the walls are made of electrolessnickel-plated mild steel.

[0063]FIG. 10A shows the power distribution board at the “rear” of thepower sub-frame (i.e. opposite to the open side). When inserted in thechassis of the system unit, this “rear” of the power sub-frame isactually the forward-most side of the power sub-frame when viewed withrespect to the system unit. The power distribution board 190 is formedwith ventilation holes 194 and carries circuit tracks and components(not shown). FIG. 10A also illustrates the flanges 198 with screw holes199 for securing the power sub-frame to the rear chassis wall.

[0064]FIG. 10B shows the top of power sub-frame. It will be noted thatthe power sub-frame body 196 is provided with apertures 197 forlightness and for ventilation purposes.

[0065]FIG. 10C shows the open (front) side 195 (see FIG. 10B) of thepower sub-frame. When inserted in the chassis of the system unit, this“front” of the power sub-frame is actually the rear-most side of thepower sub-frame when viewed with respect to the system unit. Within thepower sub-frame 72, connectors 192A, 192B and 192C for the three powersupply units 74A, 74B and 74C, respectively, can be seen. Theseconnectors are mounted on the power distribution board 190 inside thepower sub-frame 72. FIG. 10C also shows the flanges 198 with screw holes199 for securing the power sub-frame to the rear chassis wall.

[0066]FIG. 10D is a perspective view of the power sub-frame 72, whichshows that this in fact forms part of a power sub-assembly 71. Internalwalls 200 separate three compartments, each for a respective one of thethree power supply units 74. Cables 202 connect standby power and signallines from the power distribution board 190 to a connector 204 forconnection to an alarms module. Cables 206 connect main power and signallines from the power distribution board 190 to various connectors 208,210, 212 and 214. FIG. 10E shows the various connector types 192, 204,208, 210, 212 and 214 and the electrical signal connections thereto.

[0067]FIG. 11 is a schematic representation of some of the logicconnections on the power distribution board. For ease of explanation,only those connections relevant for an understanding of the presentinvention are described.

[0068] At the left of FIG. 11, the three connectors 192A, 192B and 192Cfor the three power supply units 74A, 74B and 74C are shown. For reasonsof clarity and convenience only those connections relevant for anunderstanding of the present invention as shown. For example, asillustrated with respect to FIG. 10E, the connectors 192 have many pinsand pass many signals via respective lines. However, as not all of theselines are necessary for an understanding of the present invention, andas it would be confusing to illustrate all of the signal pathways on adiagram, only selected pathways are shown in FIG. 11. It is to be notedfrom FIG. 10E, that the power supply units output ground, +3V3, +5V,+12V, −12V and +5V standby potentials as well as control signals such asPSU OK, PSU ON, etc. The +5V standby voltage is used for powering thealarm module 78. The other voltages are for powering the motherboard andother main system components. The various lines could be configuredusing bus bars, wires, printed circuit or thick film conductors asappropriate.

[0069] Firstly, the two-of-three circuit 232 will be explained. Thiscircuit is powered by the +5V standby voltage 231 provided from each ofthe power supply units 74. Each of the power supply units outputs a PSUOK signal via a pin on its respective connector to a corresponding PSUOK line 230A, 230B and 230C when the power supply unit is operatingcorrectly. Each of these PSU OK lines 230 is connected to thetwo-of-three circuit 232. This comprises three AND gates 234, 236 and238, each for comparing a respective pair of the PSU OK signals. Theoutputs of the AND gates are supplied to an OR gate 240.

[0070] If the output of this OR gate is true, then at least two of thepower supply units 74 are operating correctly, and power can be suppliedto the motherboard of the computer system. This can be achieved byclosing the main power line 245. An output signal 242 could be suppliedto a gate 244 (for example a power FET) to enable current to pass to themotherboard and other system components. Additionally, or alternatively,a power OK signal 246 for controlling some other form of switchmechanism (not shown).

[0071] If alternatively the output of the OR gate 242 is false, thenthis indicates less than two of the power supply units 74 are operative.In this case power is prevented from being passed to the motherboard 40of the computer system. This can be achieved by interrupting the mainpower line 245. An output signal 242 could be supplied to a gate 244(for example a power FET) to prevent current being passed to themotherboard and other system components. Additionally, or alternatively,a power fault signal 246 could be passed to the alarms module and/or forcontrolling some other form of switch mechanism (not shown).

[0072] One-of-three power control is effectively provided by the alarmsmodule 78 to be described later. However, with reference to FIG. 11,input A/B signals 268 and output sense signals 270 are passed to thealarms module for standby operation, and control signals 272 could bereturned for turning off of a power supply unit, if required.

[0073]FIG. 11 further illustrates a protection circuit 256 that is ableto detect an overcurrent representative of a current greater than2*Imax, where Imax is the maximum current that can be output by a powersupply, 2*Imax being the maximum current which should be required by thesystem unit. If a current greater than 2*Imax is detected, this isrepresentative of a fault in the system unit. In accordance with telcorequirements, in such a situation the system should be powered down. Byproviding for overcurrent detection on the power distribution board,where the maximum drawable current should be 2*Imax, it is possible totest for a fault at a lower overall current than if this test were madewithin each power supply unit. If the test were made in each powersupply unit, each power supply unit would need to be tested for anovercurrent in excess of Imax, whereby one would be testing for a totalcurrent drain of 3*Imax. This could lead to faults not being detected ornot detected early enough and the system could incorrectly be drawing upto 3*Imax, which could damage components and traces (tracks).

[0074] Thus, as shown in FIG. 11, each of the main power lines (e.g.,+12V) 250A, 250B and 250C from the power supply units 74A, 74B and 74C,respectively is connected to form a common power supply line 254. Anovercurrent detector 258 detects a current in excess of 2*Imax. If sucha current is detected (for example as a result of a fault represented bythe box 266), then a signal 261 is provided to the connectors 192,A,192B and 192C for shutting down the power supplies 74A, 74B and 74C,respectively. Also, a signal 262 is passed to a switchable shunt 260(e.g., a silicon controlled rectifier (SCR), a Metal Oxide SemiconductorField Effect Transistor (MOSFET), an Insulated Gate Bipolar Transistor(IGBP), etc) to shunt the power supply line 254 to ground. This willcause any energy stored in the power supplies and also in the system(for example as represented by the capacitor 264) to drain to ground,thus protecting the system.

[0075] The use of the two-of-three circuit described above means thatredundant power supply operation is provided in that the system canremain powered even if one of the three power supply units fails. Asonly two-of-three power supply units are needed to power the system thethird power supply unit can be hot swapped while the other two powersupply units power the system.

[0076]FIG. 11 illustrates the location of an alarms card forming thealarms module 78 in the rear of the system unit 10.

[0077]FIG. 12 is a functional block diagram for illustrating the alarmsub-system on the alarms module 78. The alarms sub-system provideslights out management or remote management of the system over a serialconnection. The alarms module 78 interfaces with the motherboard throughan EBus edge connector slot 298 (connected to EBus2 as shown in FIG. 8).A PCI-style bracket is attached to one edge of the alarms module (asseen in FIG. 11) and provides the external interfaces at the rear of thechassis 11. Internal interfaces provide connections to the power supplyassembly and to the LED card 80 located at the front panel of the systemunit 10. The alarms module is powered by the standby, or reserve, powersupply. The alarms module only requires power from a single power supplyto remain operable. Accordingly, the alarms module can remain operableeven in a situation where the system has been powered down due to therebeing only one power supply unit operable.

[0078] The alarms sub-system comprises a logic device 280 which receivesinputs 298 from the EBus, inputs 286 from the fans, input 290 fromgeneral purpose events, input 270 from the power supply unit outputrails and inputs 268 from the A and B power inlets. The logic circuitsamples, or multiplexes, the inputs to the microcontroller 296 inresponse to multiplex signals from the microcontroller 296. Themicrocontroller 296 processes the sampled (multiplexed) inputs. Themicrocontroller 296 provides power control signals 272 for controllingthe power supply units, and alarm outputs for the output of alarmsignals. The microcontroller 296 also outputs power supply unit statussignals 304 and fault signals 306. The micro controller 296 can furtheroutput a system reset signal 310, when required. Alarm signals to bepassed to a remote location can pass via a remote serial connection 112.Diagnostic and remote control signals can be passed from the network viathe serial connection 112 to the microcontroller 296. Control signalscan thus be provided via the remote serial connection over the networkfor powering on and powering off the system. Examples of other commandsthat can be sent to the microcontroller via the remote serial connection112 are to turn alarms off, to reset the monitoring of all failures, todisplay the status of all fans, power supply units, alarms and faultLight Emitting Diodes (LEDs), to display an event log, etc.

[0079] The microcontroller is programmed to report any fan failures orchanges in power supply units status by means of the LEDs 92 (FIG. 5) onthe system front and optionally to report the faults via the remoteserial connection 112. The microcontroller 296 is programmed to maintainthe event log that was referenced above.

[0080]FIG. 14 illustrates the configuration of the fan control module 66shown in FIG. 4. The fan control module is subdivided into two halves66A and 66B. One half 66A handles one processor fan 68A and one systemfan 70B and the other half 66B handles the other processor fan 68Bandthe other system fan 70B. The fans are connected to the fan controlmodule 66 by respective power lines 320 so that the fans receive theirpower via the fan control module. The fan control module receives +12Vpower via power lines 324A/B from the power distribution board 190 andsupplies voltages to the fans via the power lines 320 in a controlledmanner.

[0081] For convenience, tacho (speed) signals from the fans pass via thealarms control module 66. The speed signals are not processed by the fancontrol module, but are instead forwarded via tacho sense 326 to thepower distribution board 190. The power distribution board then routesthe tacho sense signals to the alarms module 78 to form the signals 286shown in FIG. 13. This routing is convenient as it enables simplerwiring looms to be used. Also, when replacing a fan unit, themaintenance engineer only needs to remove a single bundle of wires fromthe fan to the fan control module 66, rather than having to locate anumber of different connectors connected to the fan. The fan controlmodule thus has four fan connectors, each for receiving a connectorconnected to a bundle of wiring from a respective fan, plus a furtherconnector for receiving a connector with a bundle of wires from thepower distribution board.

[0082] As shown in FIG. 14, each half 66A/66B of the fan control modulereceives respective power lines 324A/B from the power distributionboard. Each half of the fan control module includes electrical noiseisolation circuitry 340A/B. This electrical noise isolation circuitry325 A/B, which can be of conventional construction, prevents dirty powersignals on the lines 320A/B caused by electrical noise from the fansbeing passed back along the power lines 324A/B and potentiallycontaminating the otherwise clean power supply to the electronics of thesystem unit (e.g., the components on the SCSI bus. The provision ofclean power supply signals in a telco application is important in orderto ensure reliability of operation. Although in the present example thenoise isolation circuitry is located in the fan control module, it couldbe located elsewhere as long as it is effective to isolate the mainpower lines from fan-related electrical noise.

[0083] As further shown in FIG. 14, each side 66A/B of the fan controlmodule comprises control logic 342A/B which receives a temperaturesignal from a temperature sensor 344 and adjusts the speed of the fansby adjusting the voltage supplied thereto in accordance withpre-programmed parameters in order to provide a desired degree ofcooling. The control logic 342A/B can be implemented by an ASIC, aprogrammable logic array, or any other appropriate programmable logic.Alternatively, it could be implemented by software running on amicrocontroller or microprocessor module.

[0084] It should be noted that the fan control module could beimplemented in a unitary manner, rather than being divided into twohalves. Although in the present instance the fan control module ispreferably configured on a single circuit board, this need not be thecase. Also, although the temperature sensor is also mounted on the samecircuit board, it could be mounted elsewhere. Moreover, although it ispreferred that a single temperature sensor is used, with the advantagethat the fan speeds of the respective fans can be ramped up in parallelin a controlled manner, more than one temperature sensor could be used.Ideally, in this case they would be located close together and controlof the individual fans could be dependent on individual signals butwould more preferably be dependent on a function of some or all of thetemperature signals. As a further feature, the control logic could beprovided with different sets of programmed parameters depending on thenumber of processors present and could be responsive to the number ofprocessors present.

[0085] It will be appreciated that although particular embodiments ofthe invention have been described, many modifications/additions and/orsubstitutions may be made within the spirit and scope of the presentinvention. Accordingly, the particular example described is intended tobe illustrative only, and not limitative.

What is claimed is:
 1. A fan control module for a system unit, the fancontrol module comprising power outputs for supplying power to aplurality of fans, a temperature sensor for giving a temperature signal,and a control unit connected to receive the temperature signal andincluding preprogrammed control information for determining powersignals to be supplied to each of the fans for controlling the speedthereof dependent upon the temperature signal.
 2. The fan control moduleof claim 1, comprising at least one power input for receiving power froma power supply, the fan control module including electrical noiseisolation circuitry to isolate system components from electrical noisegenerated by the fans.
 3. The fan control module of claim 1, comprisinga first part for controlling a first pair of fans, the first partcomprising respective first power outputs for supplying power to thefirst pair of fans, and a first control unit connected to thetemperature signal from the temperature sensor and including firstpreprogrammed control information for determining first power signals tobe supplied to each of the first pair of fans for controlling the speedthereof dependent upon the temperature signal; and a second part forcontrolling a second pair of fans, the second part comprising respectivesecond power outputs for supplying power to the second pair of fans anda second control unit connected to the temperature signal from thetemperature sensor and including second preprogrammed controlinformation for determining second power signals to be supplied to eachof the second pair of fans for controlling the speed thereof dependentupon the temperature signal.
 4. The fan control module of claim 3,wherein the first and second information is identical.
 5. The fancontrol module of claim 3, comprising one power input for receivingpower from a power supply for the first part, the first part includingfirst electrical noise isolation circuitry to isolate system componentsfrom electrical noise generated by the first pair of fans, and a secondpower input for receiving power from a power supply for the second part,the second part including second electrical noise isolation circuitry toisolate system components from electrical noise generated by the secondpair of fans.
 6. The fan control module of claim 1, wherein a first fanis a system fan for drawing air into the system unit and a second fan isa processor fan for driving air over a processor module in the systemunit.
 7. The fan control module of claim 3, wherein a first fan of eachpair of fans is a system fan for drawing air into the system unit and asecond fan of each pair of fans is a processor fan for driving air overa processor module in the system unit.
 8. The fan control module ofclaim 1, configured on a circuit board.
 9. The fan control module ofclaim 1, wherein speed signals from each of the fans are passed via thefan control unit.
 10. A system unit including a fan control module, thefan control module comprising power outputs for supplying power to aplurality of fans, a temperature sensor for giving a temperature signal,and a control unit connected to receive the temperature signal andincluding preprogrammed control information for determining powersignals to be supplied to each of the fans for controlling the speedthereof dependent upon the temperature signal.
 11. The system unit ofclaim 10, wherein the fan control module comprises at least one powerinput for receiving power from a power supply, the fan control moduleincluding electrical noise isolation circuitry to isolate the powersupply from electrical noise generated by the fans.
 12. The system unitof claim 10, wherein the fan control module comprises a first part forcontrolling a first pair of fans, the first part comprising respectivefirst power outputs for supplying power to the first pair of fans and afirst control unit connected to receive the temperature signal from thetemperature sensor and including first preprogrammed control informationfor determining first power signals to be supplied to each of the firstpair of fans for controlling the speed thereof dependent upon thetemperature signal; and a second part for controlling a second pair offans, the second part comprising respective second power outputs forsupplying power to the second pair of fans and a second control unitconnected to receive the temperature signal from the temperature sensorand including second preprogrammed control information for determiningsecond power signals to be supplied to each of the second pair of fansfor controlling the speed thereof dependent upon the temperature signal.13. The system unit of claim 12, wherein the first and secondinformation is identical.
 14. The system unit of claim 11, wherein thefan control module comprises one power input for receiving power from apower supply for the first part, the first part including firstelectrical noise isolation circuitry to isolate system components fromelectrical noise generated by the first pair of fans, and a second powerinput for receiving power from a power supply for the second part, thesecond part including second electrical noise isolation circuitry toisolate system components from electrical noise generated by the secondpair of fans.
 15. The system unit of claim 10, wherein a first fan is asystem fan for drawing air into the system unit and a second fan is aprocessor fan for driving air over a processor module in the systemunit.
 16. The system unit of claim 10, wherein a first fan of each pairof fans is a system fan for drawing air into the system unit and asecond fan of each pair of fans is a processor fan for driving air overa processor module in the system unit.
 17. The system unit of claim 10,wherein the fan control module is configured on a circuit board.
 18. Thesystem unit of claim 17, wherein speed signals from each of the fans arepassed via the fan control unit.
 19. The system unit of claim 10,wherein the system unit is a computer system unit including at least oneprocessor module.
 20. The system unit of claim 19, including up to fourprocessor modules.
 21. The system unit of claim 19, wherein the signalsoutput b the control unit is dependent upon the number of processormodules present.
 22. The system unit of claim 10, rack mountable in arack.
 23. A method of controlling cooling of a system unit, the methodcomprising: a fan control module a temperature signal from a temperaturesensor; the fan control module determining power outputs to the fans forcontrolling the speed thereof dependent upon the temperature signal fromthe temperature sensor in accordance with preprogrammed controlinformation.
 24. The method of claim 23, further comprising the fancontrol module receiving power from a power supply, and the fan controlmodule providing electrical noise isolation to isolate system componentsfrom electrical noise generated by the fans.
 25. The fan control moduleof claim 23, wherein the fan control module individually controls thespeed of two pairs of fans with a respective control loop being providedfor each pair of fans.
 26. The method of claim 23, wherein the fancontrol module individually controls the speed of a first fan fordrawing air into the system unit and a second fan for driving air over aprocessor module in the system unit.
 27. The method of claim 25, whereina first fan of each pair of fans is a system fan for drawing air intothe system unit and a second fan of each pair of fans is a processor fanfor driving air over a processor module in the system unit.